Supplementation with n-3 and n-6 polyunsaturated fatty acids: Effects on lipoxygenase activity and clinical symptoms of pruritus in hemodialysis patients

Efficacy and Safety of Omega-3 Fatty Acids in Ameliorating Pruritus in Adult Patients With Chronic Kidney Disease: A Meta-Analysis of Randomized Controlled Trials

Chronic kidney disease-associated pruritus (CKD-aP) represents a common distressing problem in patients with end-stage renal disease. This study aimed to assess the efficacy and safety of omega-3 supplementation in the treatment of CKD-aP. MEDLINE/PubMed, Cochrane Central Register of Controlled Trials, Web of Science, ProQuest, and Scopus databases were searched systematically for articles published from inception until May 21, 2024. Outcomes were pruritus severity at the end of the study or its change from baseline (primary) and intervention-related adverse effects (secondary). Results were pooled as standardized mean difference (SMD) and risk ratio (RR) for numeric and dichotomous outcomes, respectively, along with their 95% confidence intervals (CIs). Eight studies were included. Treatment with omega-3 fatty acids showed a significantly lower severity of CKD-aP at the end of treatment (pooled SMD (95% CI) = -1.03 (-1.85, -0.22), p = 0.024) and changed from baseline (pooled SMD (95% CI) = -0.93 (-1.57, -0.28), p = 0.014). Omega-3 supplementation reduced the risk of CKD-aP (pooled RR (95% CI) = 0.68 (0.12, 3.81), p = 0.661). Omega-3 fatty acid supplementation appears to be a promising effective and safe treatment for CKD-aP. However, the included studies had several limitations that warrant further high-quality studies to elucidate its effect and investigate the causes of non-response in patients who did not improve.

Pruritus-reducing effects of omega-3 fatty acids in hemodialysis patients: A cross-over randomized clinical trial

INTRODUCTION

Chronic kidney disease-associated pruritus is a common complication in patients with end-stage renal disease. In this study, we have explored the outcome of omega-3 supplementary intake for the treatment of this symptom.

METHODS

This double-blinded, randomized, crossover study was conducted in two dialysis centers in which 40 hemodialysis patients suffering from pruritus were randomly assigned into two groups (Group A and Group B). Patients in Group A consumed omega-3 capsules for 4 weeks and after a washout period (6 weeks), they took placebo for another 4 weeks. The same was performed in Group B but in the reverse order. Pruritus score was determined at the baseline, Week 4, 10, and 14. Serum levels of prostaglandin E2 were also recorded at the baseline and Week 4.

RESULTS

There was a statistically significant reduction of pruritus score in patients who took the omega-3 fatty acid supplement. The mean pruritus score decreased significantly in both first (-3.41 ± 2.62, p < 0.001) and second (-1.00 ± 1.84, p = 0.04) treatment period after omega-3 treatment; but no significant mean pruritus score difference in placebo group after both intervention periods was observed. The decrease in prostaglandin E2 amount was not statistically significant in the intervention (omega-3) group compared to the placebo group (p = 0.204).

DISCUSSION

Our observations indicate that omega-3 fatty acids (3 grams per day) have decreasing effects on pruritus. Also, reduction in prostaglandin E2 levels in the omega-3 group did not differ from the changes in the placebo group.

Essential polyunsaturated fatty acids, inflammation and mortality in dialysis patients

BACKGROUND

Polyunsaturated fatty acids (PUFA) are essential nutrients with anti-inflammatory and cardioprotective properties. We investigated the association of essential dietary PUFA intake, reflected by plasma fatty acid composition, with inflammation and mortality in dialysis patients.

METHODS

We recruited 222 Swedish dialysis subjects (39% women) with median age of 57 years and average 12 months of dialysis vintage. Plasma phospholipid PUFA were assessed by gas-liquid chromatography. Overall mortality was assessed after 18.4 (10th-90th percentiles: 2.3-60) months of follow-up.

RESULTS

Linoleic acid (LA), Mead acid (MA), α-linolenic acid (ALA) and long-chain n-3 PUFA (LC n-3; the sum of eicosapentaenoic, docosapentaenoic and docosahexaenoic acids) represented 19.7, 0.26, 0.26 and 7.64% of all fatty acids in plasma, respectively. This may reflect an adequate n-3 PUFA intake. LA was negatively (β = - 0.21, P = 0.004) but MA positively (β = 0.25, P < 0.001) associated with interleukin (IL)-6 in multivariate analyses. Neither ALA nor LC n-3 were independently associated with IL-6. During follow-up, 61 deaths and 115 kidney transplants occurred. Fully adjusted competing risk models showed that every percent increase in the proportion of plasma LA was associated with 12% reduction in mortality risk before transplantation (hazard ratio 0.88, 95% confidence interval 0.79-0.99). MA was directly associated with mortality. Neither ALA nor LC n-3 predicted outcome.

CONCLUSIONS

The proportion of plasma phospholipid LA is inversely associated with IL-6 and all-cause mortality in Swedish dialysis patients. We raise the hypothesis that dialysis patients could benefit from increased intake of vegetable oils, the primary source of LA in the Western-type diet.

Review of the Effects of Omega-3 Supplementation in Dialysis Patients

Chronic dialysis patients experience a host of conditions that limit quality and length of life, and recent therapeutic strategies have had only modest success in ameliorating many of these problems. By mediating cell membrane function and structure and the synthesis of lipid mediators such as eicosanoids, omega-3 fatty acids may offer dialysis patients a host of therapeutic benefits. Omega-3 fatty acids are derived primarily from dietary sources, and cold-water fish is the main source of eicosapentanoic and docosahexanoic acids, the two major bioactive omega-3 fatty acids. Studies of omega-3 supplementation in dialysis patients describe salutary effects on triglyceride levels, dialysis access patency, and perhaps uremic pruritus and oxidative stress. In contrast, the putative hematologic, antihypertensive, anti-inflammatory, and antiarrhythmic effects are not as well documented. Adverse effects generally have been limited to gastrointestinal complaints. Unfortunately, the preponderance of published studies are characterized by suboptimal study design, small sample sizes, supraphysiologic omega-3 doses that may be difficult to consume for extended periods, little long-term follow-up, and a lack of confirmation of compliance. Not surprising, the 2005 National Kidney Foundation Kidney Disease Outcomes Quality Initiative Clinical Practice Guidelines for Cardiovascular Disease in Dialysis Patients recommend further research in this field. In summary, although preliminary data suggest that omega-3 fatty acids may have clinical benefits, formal recommendations encouraging omega-3 supplementation of dialysis patients are premature until long-term and adverse effects are better defined.